For the most part, we make decisions based on our prior experiences. But what about those situations that are completely new or unpredictable? A new study suggests that when facing an excessively uncertain or challenging scenario, the brain chooses randomness as the best strategy.

When it comes to making decisions, our brains are extremely dependent on past experiences. In fact, some cognitive scientists speculate that the brain has a built-in mechanism for assessing (or weighing) the efficacy of a decision based on precedents from the past. It's also something we can be conscious of; to improve our rational decision making, it's important that we use new information to change our confidence in a belief. But as a recent experiment conducted by Alla Karpova of the Janelia Farm Research Campus shows, randomness may be the brain's preferred policy when things get particularly challenging or when the situation is completely without precedent.

This isn't necessarily good, however. It can lead to risk-taking, and worse, learned helplessness.

Random Decision Making Mode

Karpova's experiment showed that rats, when facing a competitor that's hard to defeat, will abandon their normal tactic of using past experience to make decisions and will instead make random choices. This switch in strategy, she says, is controlled by a dedicated brain circuit — an indication that the brain can actively disconnect from its past experiences and enter into a kind of random decision making mode in a desperate attempt to confer a competitive edge.

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This actually makes sense from an evolutionary perspective. When animals encounter new and unpredictable situations — like when in a completely new environment, stuck, or facing prey that moves erratically — it's often beneficial to vary behavior randomly. This can lead to risky decisions that wouldn't otherwise be attempted, and even a kind of "out of the box" thinking. Trouble is, it's often difficult for some animals to get out of this mode, which can be interpreted as being maladaptive.

A Kind Of Learned Helplessness

For the experiment, Karpova's team trained rats to stick their nose in one of two ports to potentially receive a sweet reward. A computer-simulated competitor, which was programmed to analyze past experiences to predict future choices, monitored the rats. That rats received the reward only when their chosen port was different from that predicted by the computer. When the competitor was weak, the rats made choices based on past experiences (as usual). But when a tough competitor used complex algorithms to make strong predictions based on subtle behavioral patterns, the rats ignored their past experiences and instead selected the ports at random. In fact, many of them got stuck in this mode — a behavior reminiscent of learned helplessness.

Karpova says the mechanism behind this change is found in the anterior cingulate cortex (ACC), a brain structure involved in using experience to make decisions. And in fact, when the researchers manipulated the activity of neurons that released a stress hormone into the ACC, they were able to reverse the rats' behavioral strategies. When these neurons were stimulated, the rats abandoned the experience-based strategy and started to behave randomly in situations when this wasn't expected. Fascinatingly, inhibition of the stress hormone, norepinephrine, caused the rats to rely on their experiences — even when faced with the challenging competitor.

Implications for Humans and the Treatment of Depression

As always, studies on rats need to be taken with a grain of salt. But as Karpova points out in her paper, "when faced with virtual competitors, primates resort to strategic counterprediction rather than to stochastic choice." So it's very likely that we're also prone to these cognitive processes.

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So needless to say, these findings could inspire some interesting and related areas of research. For example, Karpova's paper, which now appears in Cell, may have implications for the treatment of human disorders such as depression.

"We discovered that animals can get stuck in a random mode of behavior that in a way resembles learned helplessness, which has been linked to depression and is triggered when repeated efforts prove to be ineffective," said Alla Karpova in an accompanying release. "Our findings may shed light on the origins of learned helplessness and the associated impairments in strategic decision-making."

Her findings suggest that changes in the ACC could prevent erroneous beliefs from guiding decisions and promote exploratory behavior when environmental rules are uncertain.

"But sometimes these changes in neural activity can go too far and become maladaptive, resulting in learned helplessness or even depression," she says. "In those cases, suppression of norepinephrine release into the anterior cingulate cortex may serve as an effective therapy to restore strategic decision-making."